Apparatus for burning oil with a high carbon to hydrogen ratio



16, 1966 w. SICK ETAL 3,266,550

iAPPARATUS FOR BURNING OIL WITH A HIGH CARBON TO HYDROGEN RATIO Filed Dec. 11, 1962 F/G.7 2b 2c MR 9 /I/:\\\ 42 V 41 75 F/G.3 6

INVENTORS 1 WALTER SICK HANS Z lRNG/BL W? I PNEY ATTO United States Patent 3,266,550 APPARATUS FOR BURNING 01L WITH A HIGH CARBON TO HYDROGEN RATIO Walter Sick, Cologne-Bruck, and Hans Zirngibl, Duisburg,

Germany, assignors to Farbenfabrilten Bayer Aktieugesellschaft, Leverkusen, Germany, a corporation of Germany Filed Dec. 11, 1962, Ser. No. 243,812 Claims priority, application Germany, Apr. 4, 1959,

6 Claims. (c1. 1ss-4 This is a continuation-in-part of application Serial No. 18,338, filed March 29, 1960, now abandoned.

The present invention relates to an improved process for burning oil with a high carbon to hydrogen ratio.

Processes for burning oil having a high carbon to hydrogen ratio are known in which processes the liquid fuel is injected axially into an axially-symmetrical combustion chamber, which is constricted at the inlet and outlet ends, the air and burnt gases fiowing through the chamber in a spiral rotational vortex around the mean axis, a return flow of the burnt gases being set up in the vicinity of the chamber axis and this flow being directed towards the stream of injected fuel. US. patent to Kerrick, 2,284,- 906, discloses such apparatus.

It has been found in practice that the known processes and constructions are not suflicient in order to ensure that the combustion is practically soot-free, as required industrially when using types of heavy oils, for example bunker-C-ofl. Thus, oil burners which are available on the market and which operate in a system with direct heat exchange, are not adequate for drying, evaporation and melting processes when using materials which are sensitive to carbon. The reason for the incomplete combustion of oils having a high carbon to hydrogen ratio is attributed to the fact that the oil drops are too large and the mixing speeds are too low.

The present invention is concerned With a process for the combustion of oils having a high carbon to hydrogen ratio, in which the liquid fuel is injected axially into an axially symmetrical combustion chamber which is constricted at the inlet and outlet ends, through which chamber the air and burnt gases flow in a spiral rotational vortex about the mean axis, a return stream of the burnt gases being set up in the vicinity of the chamber axis, this stream being directed towards the stream of injected fuel, wherein the return stream velocity in the combustion chamber and the degree of fineness of the atomization of the injected fuel stream are so matched to one another that the return flow retards the injected fuel stream in the region of the fresh air supply inlet and introduces the retarded stream into the surrounding rotational vortex. According to one preferred form of the invention, the fuel is injected with a pressure of more than 100 atm., preferably 150 to 300 atm., at a spray-angle of about 2090, preferably 3060, and the combustion chamber is operated with a specific loading of more than 10x10 lc.cal./h.m. preferably S0 l0 k.cal./h.m. To facilitate operation as described, the burner of the invention is provided with a conical bafile at the inlet. The conical bafile is arranged so that it provides the desired mixing of air and fuel.

The effect obtained hereby is that the return flow 1'e tards the injected stream in the vicinity of the fuel inlet aperture, and the retarded stream is passed into the outer zone of the vortex. In order to obtain favourable operating conditions, the ratio between tangential and axial speeds of the air on the radius of the air inlet aperture is preferably adjustedto be smaller than 1. By this means, both the preparation and the combustion of the oil can be so conducted within a hot flame zone that the combustion 3,266,550 Patented August 16, 1966 is of such high perfection as could not be obtained in the prior art processes. In this way, the total quantity of the carbon-containing residue in the exhaust gas is far below the limit which can be detected optically. It has also been found that, with extremely careful washing of the burnt gases under reproducible working conditions, there only remained a soot and carbon residue of 0.02%, based on the quantity of oil which was burnt. Due to the high injection pressure, the drops of oil are broken up into a mist of utmost fineness. Owing to the large surfaces produced thereby, extremely high vaporisation and combustion speeds are obtained. With the high loading of the combustion chamber according to the present invention, the return flow velocity necessary for the extremely quick mixing increases and the temperature is sutficient for the extremely fast burning.

According to the invention, apparatus for burning oil comprises an axially symmetrical elongated combustion chamber having an axially disposed, constricted, inlet opening for oil and air at one end thereof and an axially disposed, constricted, outlet opening for burnt gases at the other end thereof. Further the apparatus comprises oil inlet means for dispersing oil in a spray adjacent the oil inlet, and said oil inlet means is axially positioned within the inlet opening spaced from the periphery thereof. Also included is a conically shaped bafile axially positioned about the oil inlet means adjacent the inlet opening with its vertex end disposed Within the inlet opening. The convergence of the baffle cone is about 7 0-110", preferably about The batfie with said inlet opening defines an annular air inlet. The area of the annular air inlet is about 30-50% of the area of said inlet opening. The apparatus can include means for whirling air through the air inlet for admixing air and oil, and the chamber and its'inlet opening and outlet opening are constructed so that the gas flows in the chamber in a spiral rotational vortex about the chamber axis and a return stream of burnt gas flows adjacent the chamber axis from adjacent the outlet toward the inlet.

An apparatus for carrying out the process consists of an axially symmetrical combustion chamber constricted at the inlet and outlet ends, in which the ratio between the diameter of the inlet aperture and that of the outlet aperture is about 1:15 to 1:25, and in which the ratio between the diameter of the inlet opening and the largest diameter of the combustion chamber is about 1:3 to 1:5, preferably 1:4. The fuel nozzle is arranged coaxially to the air inlet aperture or at a small distance below the air inlet aperture in the combustion chamber. The length of the combustion chamber should not be smaller than the largest diameter of the chamber.

The above-mentioned conical bafiie facilitates the fine setting of the ratio between the tangential and axial speed of the entening air. For this purpose the conical bafile or displacement member is axially adjustable. The variable adjustment between axial and tangential speeds contributes to the extremely intensive and rapid mixing. Moreover, the return flow towards the nozzle is deflected in the vicinity of the air inlet aperture by the movably arranged displacement member.

This is extremely important in respect of the high loading (high heat release rate) of the combustion chamber since otherwise the return flow, which still contains drops of oil in the liquid state, projects these drops onto the nozzle and the cold walls around the inlet aperture there- 'by causing crust formation around the fuel nozzle and in the combustion chamber.

A device for producing the tangential velocity of the air for combustion can be formed in various ways. It can for example consist of an arrangement of adjustable louvres or it can be produced by providing fixedly ar-' ranged guide vanes on the wall of the housing or combustion chamber.

An additional advantage of the invention consists in that the outlet aperture of the combustion chamber can be used as a throttling means for producing higher pressures during the combustion.

The process of the invention can also be used for pres sure firing systems, the small size of the combustion chamber providing an important advantage over other constructions from the point of view of danger of explosion. By using this process for pressure firing systems, it is possible to operate with equal success with a higher load (heat release rate) in the combustion chamber, this load corresponding to the pressure level. It is immaterial whether the pressure drop origin-ates from an apparatus which is to be heated or by throttling at the combustion chamber outlet.

One example of an apparatus for carrying out the process is shown diagrammatically in the accompanying drawing, FIG. 1 being a longitudinal section through the apparatus and FIG. 2 a plan view thereof. FIG. 3 is a view of part of the apparatus shown in FIG. 1.

In the drawing, 1 represents an axially symmetrical combustion chamber with constricted inlet and outlet ends. The reference 2 represents a member having a frustro-conical end 2a, which member extends from above, axially into the inlet opening 10a of the combustion chamber, and which is adjustable axially during operation by threading the threads 211 through the support block 20. The ignition device 4 can be arranged in this displacement member 2. The displacement mem ber 2 is so designed that the oil nozzle 3, in the operating position, is disposed substantially at the end of the air inlet aperture 10, i.e. at the height of the commencement of the conical enlargement 1 1 of the combustion chamber 1. The comcombustion chamber 1 is enclosed by a spiral housing 7 into which the air for combustion flows through the pipe 6. The air for combustion is set in rotation in the spiral housing 7 and enters the space 9 of the housing over the edge 8. Guide vanes 12 are arranged in the space 9 to control the rotation. The air set in rotation enters the axially symmetrical combustion chamber 1 through the inlet aperture 10. It maintains its rotational movement in the combustion chamber. Due to the rotational movement, a return flow 13 is produced, by which the stream of fuel 14, injected from the nozzle 3, is retarded near the fresh air inlet 10. The retarded fuel particles are dis persed, vaporised or gasified by the rotating return flow 13 and are completely burnt on coming into contact with the air for combustionentering through the aperture 10. Some of the circulating burnt gases leave the combustion chamber 1 continuously through the opening .15 at the rate at which combustible oil and air for combustion are introduced through the nozzle 3 and the aperture 10, respectively. In order to be able to adjust the flow condi tions, the combustion chamber 1 is displace-ably arranged in the housing 5 and is brought by adjusting screws 16 to the accurate position in relation to the displacement member 2 and the nozzle 3.

Using a conical bafile or displacement member according to the invention, it was found that at high loads even above 100 10 k. ca1./'m. h., for prolonged operation, no incrustations occur.

The structure of the invention provides a return stream of the combustion gas, the outside diameter of which depends exclusively on the ratio of the tangential component to the axial component of the fresh air entering at The entering air hits the conical baffle, is deflected laterally upward and again returned into the combustion chamber by the entering fresh air. The conical baflie provides a turning around of the return stream which is more favorable to the flow system. The larger droplets formed in the atomizing of the oil penetrate, corresponding to their greater mass, more deeply into the return stream, wherein they rapidly evaporate and/ or gasify, because of high relative velocity and high temperature difference. Vapors, gases and carbon are pulled along by the return stream and turned around at the conical bafiie, and seized by the fresh air, which carries them into the outer zones of the combustion chamber, in which bu-rning occurs. Thus the format-ion of soot is practically completely avoided.

The small droplets formed in the atomization, turn around under the influence of the return stream shortly behind the nozzle-mouth, and are also turned around at the conical baffle at the place which corresponds to the outer diameter of the return stream, and seized by the fresh air.

The arrangement of the displacement member 2 with respect to the combustion chamber is illustrated in FIG. 3. The displacement member 2 provides the conical .bafiie 2a and the baffie vertex end is disposed within the inlet opening, 10a. The angle of convergence alpha of the baffle cone is about 70-1 10", preferably The baffle with the inlet opening 10a defines the annular air inlet 10, and the area of the annular air inlet 10- is about 30-50% of the area of the inlet opening 10a, i.e., the area of the annulus defined by diameter y of the conical baffle and the diameter x of the inlet opening is about 30-50% of the area of the inlet opening 10a (which would be the area of a circle of diameter x).

What is claimed is:

1. Apparatus for burning oil comprising axially symmetrical elongated combustion chamber means having an axially disposed, constricted, air inlet opening at one end thereof, and an axially disposed, constricted, outlet opening for burnt gases at the other end thereof, oil inlet means for dispersing oil in a spray adjacent the air inlet, said oil inlet means being axially positioned within said inlet opening spaced from the periphery thereof, a conically shaped bafile axially positioned about the oil inlet means adjacent said inlet opening with its vertex end disposed Within said inlet opening, the convergence of the baflie cone being about 70-110", said bafiie with said inlet opening defining an annular air inlet, the area of said annular air inlet being about 30-50% of the area of said inlet opening, means for whirling air through the air inlet for admixing air and oil, said chamber means and its inlet opening and outer opening permitting the gases to flow in a spiral rotational vortex about the chamber axis and to provide a return stream of burnt gas adjacent the chamber axis, the ratio between the diameter of said inlet opening and said outlet opening for burnt gases being about 1:15 to 1:25, and the ratio between the diameter of said inlet opening and the largest diameter of the combustion chamher being about 1:3 to 1:5.

2. Apparatus according to claim 1, said convergence of the baflie cone being about 90".

3. Apparatus according to claim 1, said conical bafilc being axially adjustable relative to said chamber.

4. Apparatus for burning oil comprising an axially symmetrical elongated combustion chamber having an axially disposed, constricted air inlet opening at one end thereof, and an axially disposed, constricted outlet opening for burnt gases at the other end thereof, oil inlet means for dispersing oil in a spray adjacent the air inlet, said oil inlet means being axially positioned within said inlet opening spaced from the periphery thereof, a conically shaped bafiie axially positioned about the oil inlet means adjacent said inlet opening with its vertex end disposed within said inlet opening, the convergence of the baffle cone being about 70-110, said baffle with said inlet opening defining an annular air inlet, the area of said annular air inlet being about 30-50% of the area of said inlet opening, the ratio between the diameter of said inlet opening and said outlet opening being about 1:15 to 122.5, and the ratio of said inlet opening to the largest diameter of said combustion chamber being about 1:3 to 1:5.

5 6 5. Apparatus according to claim 3, the convergence FOREIGN PATENTS of the baflie cone being about 90.

1,148,255 6/1957 France. 6. Apparatus according to claim 4, said baflie being 762,620 11/1956 Great Britain.

axially adjustable relative to said chamber.

References Cited by the Examiner UNITED STATES PATENTS JAMES W. WESTHAVER, Examiner.

2,284,906 6/ 1942 Kerrick 158--4 E. G. FAVORS, Assistant Examiner. 2,986,206 5/1961 Boelsma 1584 0 FREDERICK L. MATTESON, JR., Primary Examiner. 

1. APPARATUS FOR BURNING OIL COMPRISING AXIALLY SYMMETRICAL ELONGATED COMBUSTION CHAMBER MEANS HAVING AN AXIALLY DISPOSED, CONSTRICTED, AIR INLET OPENING AT ONE END THEREOF, AND AN AXIALLY DISPOSED, CONSTRICTED, OUTLET OPENING FOR BURNT GASES AT THE OTHER END THEREOF, OIL INLET MEANS FOR DISPERING OIL IN A SPRAY ADJACENT THE AIR INLET, SAID OIL INLET MEANS BEING AXIALLY POSITIONED WITHIN SAID INLET OPENING SPACED FROM THE PERIPHERY THEREOF, A CONICALLY SHAPED BAFFLE AXIALLY POSITIONED ABOUT THE OIL INLET MEANS ADJACENT SAID INLET OPENING WITH ITS VERTEX END DISPOSED WITHIN SAID INLET OPENING, THE CONVERGENCE OF THE BAFFLE CONE BEING ABOUT 70-110*, SAID BAFFLE WITH SAID INLET OPENING DEFINING AN ANNULAR AIR INLET, THE AREA OF SAID ANNULAR AIR INLET BEING ABOUT 30-50% OF THE AREA OF SAID INLET OPENING, MEANS FOR WHIRLING AIR THROUGH THE AIR INLET FOR ADMIXING AIR AND OIL, SAID CHAMBER MEANS AND ITS INLET OPENING AND OUTER OPENING PERMITTING THE GASES TO FLOW IN A SPIRAL ROTATIONAL VORTEX ABOUT THE CHAMBER AXIS AND TO PROVIDE A RETURN STREAM OF BURNT GAS ADJACENT THE CHAMBER AXIS, THE RATIO BETWEEN THE DIAMETER OF SAID INLET OPENING AND SAID OUTLET OPENING FOR BURNT GASES BEING ABOUT 1:1.5 TO 1:2.5. AND THE RATIO BETWEEN THE DIAMETER OF SAID INLET OPENING AND THE LARGEST DIAMETER OF THE COMBUSTION CHAMBER BEING ABOUT 1:3 TO 1:5. 